This study aimed to test our hypothesis that a fall of blood pressure (BP) attenuates flow-mediated dilation (FMD) as an index of endothelial function in healthy young men. Eleven men (age: 21.9±0.5 yrs, body mass index: 22.4±0.5 kg/m2, mean±SE) participated in this study. We measured brachial FMD in normal FMD protocol (control trial) and protocol with a fall in BP via thigh-cuff deflation technique (BP fall trial) in a random order. During FMD measurements, brachial arterial diameter and blood velocity were recorded simultaneously using Doppler ultrasound. FMD was calculated on the basis of the percentage increase in the arterial diameter followed by cuff release. To adjust the effects of shear rate (SR) on FMD, we calculated Normalized-FMD. Mean arterial pressure during hyperemia showed a marked fall in the BP fall trial (-24±2 mmHg), but no change in the control trial. FMD was smaller in the BP fall trial than the control trial (P<0.001, Control; 7.3±1.0%; BP fall, 3.6±0.5%). Normalized-FMD also showed smaller FMD in the BP fall trial than the control trial (P=0.004). These results indicate that arterial pressure is a key factor to regulate endothelial function in young adults.
